In vitro ef fi cacy testing of ivermectin against Tritrichomonas foetus trophozoites

There are no recommended drugs to treat cattle infected with the protozoan Tritrichomonas foetus (TF). Ivermectin, widely used in the treatment of intestinal parasites, was found effective against some protozoa growing in vitro. Here, its effectiveness against a TF line was investigated. Trophozoites were incubated in media with increasing concentrations of ivermectin and mortality was determined after 24 h. Ivermectin killed cells with a mean maximum effective concentration (EC50) of 2.47 mu g mL-1. The effective concentration of ivermectin was rather high for a formulation suitable for systemic treatment. However, topical treatment of animals against TF could still be considered and tested.